|Table of Contents||A Closer Look at the Pipes||Pitch Levels||Sound Characteristics of Stops|
Lack of space in the room is often a problem for organ builders as pipes for some stops can be as large as 32' tall. Sometimes, pipes are too tall to fit in the room. Sometimes builders solve this problem by laying the pipes on their sides if the space is wide enough to do this. Another solution is mitering the pipe. This picture shows some mitered pipes. The length is the same but the top of the pipe has been folded so it can fit in the room.
Another solution is to use stopped pipes instead of open pipes. This cuts the length in half. Most 32' flute stops use stopped pipes. Many practice room organs, which must fit into a much smaller space than church or concert instruments, use stopped pipes on the 16' stops.
Stops Are Divided into Groups
Different stops are controlled by the different keyboards and the pedal board. Each manual controls one division and the pedal is also one division. On the manuals, the organist has stops from 16' to 1' available. There are usually only one or two 16' stops. A large organ may have more, but the number of 8' stops is always greater than the number of 16' stops. This is necessary because if there were more 16' stops sounding than 8' stops, the fundamental pitch (the 8') would be overshadowed by the 16'.
The pedal has a heavier concentration of 16' stops than the manuals because the pedal has a different function in organ music. It can have higher pitched stops such as 4' and 2' as well. Room space often dictates the number of stops an organ can have so if there is not enough room for a lot of pedal stops, the pedals may only have 16' and 8' stops available. A large organ may include solo stops in the pedal division. There are many pieces throughout the history of organ literature in which the pedal uses a solo stop to play the melody.
Couplers allow stops from different divisions to be played by a single manual. It is similar to a copy command in a word processing program. For more on couplers, see A Closer Look at the Console.
The choice of stops and couplers which the organist uses in a piece of music is the registration. Some composers specify the stops to be used. If the organ does not have the same exact stop names that the composer wants, the organist substitutes a similar stop. For example, principal pipes have many different names so if the composer asks for an 8' Open Diapason, an 8' Montre can be substituted. The Montre does have a different tonal quality than the Open Diapason but they are close enough so that the musical effect is still close to what the composer wanted. However, substitution does not always work well. Some organ works use so many stops that they can only be played on large organs. The organist learns how to make registration decisions through experience. Learning how to register a piece is just as important as learning how to play the notes.
It is common to use several stops at once. Some combinations of stops are so commonly used that they have names. Sometimes composer simply use the registration term instead of naming all the stops used. Here are some examples.
Chorus: Just as a choir is a mix of different voice ranges (soprano, alto, tenor, and bass), a chorus on the organ is a mix of different pitch levels. Choruses are usually 8', 4', and 2' pipes. A flute chorus uses these flute stops of these pitch levels. A principal chorus uses principal pipes of these levels and also uses the compound or mixture (labeled with a Roman numeral).
Foundations: This is the opposite of a chorus. Foundations use all 8' stops in the manuals, except the celestes, and all 8' and 16' stops in the pedal. Only flue pipes (principals, flutes, and strings) are used.
Cornet: This is an excellent example of how mutations can be effectively used. The cornet uses an 8' flute, 4' principal, 2 2/3', 2' flute or principal, and 1 3/5'. The resulting sound is like a coronet and is frequently used as a solo stop. It is not as bold as a reed stop but it has similar characteristics.
There are many more types of registration but there is not room to list all of them. Organists in graduate programs are expected to know registration so well that they cannot pass their oral exams without demonstrating knowledge of specific registrations.
Tuning a flue pipe is achieved through altering the length of the pipe. Open pipes have several methods: 1. A collar on the top is raised or lowered or 2. A metal scroll at the top is curled or uncurled. Stopped pipes are tuned by raising or lowering the stopper. The felt around the stopper ensures a tight seal but also allows the stopper to be moved. On metal pipes, you can often see the felt. The stopper is a metal cap. On wooden stopped pipes, the stopper fits like a lid on a sugar bowl so you can't see the felt from the outside. Reed pipes are tuned in the same ways as open pipes. Some closed reed pipes have a metal lid which is attached on 1/2 to 2/3 of its edges. The unattached portion can be raised or lowered. Pitch can also be adjusted through raising or lowering the tuning wire. As the wire moves, the length of the tongue allowed to vibrate changes and the pitch is affected. However, this also affects the tone so it is not the best method of tuning.
Pipe organs can go out of tune with weather changes. Temperature and humidity changes cause the pipes to expand or contract. This causes the collars and stoppers to move slightly. Reed pipes are the most stable pipes in the organ because the tongue is held tightly in place by the tuning wire and is unaffected by weather changes. Flue pipes, which have the stoppers and collars, are the culprits of poor tuning. However, they will all go out of tune at the same rate and in the same direction (sharp vs. flat). Since there are more flues than reeds in the organ, it sounds like the reeds are out of tune.
Pipe organs have a bad reputation in the United States as being constantly out of tune. All pipe organs should get one yearly complete tuning and maintenance. During the year, problem notes should be fixed as they are discovered. Despite popular belief, there are inexpensive solutions to help the organ stay in tune.
American churches do not have architecture and construction material on their side, but there are other things that can be done to keep the organ in tune.
Air Circulation: This is especially important for the pipes behind swell shades. The difference in temperature between the pipes inside the swell and the exposed pipes causes the flue pipes in these locations to expand or contract in different amounts. The swell will be out of tune with the rest of the organ. I know an organist who put fans inside all enclosed pipe divisions and now has fewer tuning problems. Allen Ontko of Ontko and Young Organ Builders solved air circulation problems when he built a large organ for First Scots Presbyterian in Charleston, SC. The organ was built into a depression in the wall. It covers a large area in the church but the deepest part of the organ only a few feet so the air circulates to all of the pipes.
I work frequently as a substitute organist so I can say from experience that organists are part of the air circulation problem. Leave the swell shoe open! Newer organs are made with a device which automatically opens when the organ is off. On older organs, this doesn't happen. A closed swell box will create tuning problems.
Temperature When Tuning: Tune the organ at the temperature the church will be when service take place. The organ will go out of tune during the week but when the church is cooled or heated for services, the organ will go back in tune. It will not be perfectly back in tune but the difference is not noticeable to most people.
Maintaining The Temperature During The Week: Do what you can to keep the temperature from fluctuating between extremes. One church in Bronxville, NY found that the energy bill was lower when they kept the church at 50 degrees Fahrenheit during the week in the winter than it was to let the temperature drop into the 20s and heat the room back up to 68 F on Sunday morning. A pleasant side effect was a more stable organ.
For those of you in hot summer climates, it may not be possible to keep the church temperature constant but the less extreme the temperature change, the more the organ will stay in tune. Air conditioning is not always necessary to control temperature. Just circulating the air near the pipes with fans will do alot to help. Also consider dehumidifiers but carefully think out how they will be emptied. You do not want water to spill on the organ!
Tune the Reeds to the Flues: My first organ teacher was an organ professor at Houghton College in Houghton, NY. The organ was used several times a week for chapel services so tuning was very important. After a sudden weather change, my professor would tune the reeds to the flue pipes as a temporary fix. However, DO NOT ALLOW an inexperienced person to do this or they will ruin your organ.
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